> When used with a Southbidge a MPC8640/8641 design can incorporate PCI slots.

Yes, but so can a QorIQ P5 design (and any other design based on a chip with an interface a southbridge can be attached to), so that's no difference between the two. And of course it doesn't need a southbridge chip for this. A PCIe-to-PCI bridge chip would do well. With the QorIQ P5 in x4 x4 x1 x1 PCIe configuration you could use one x1 to bridge to a PCI slot.